Domain Upgrade Method in Digital Rights Management

1. A domain upgrade method for a terminal, comprising: receiving, by a terminal which has a first rights object (RO) and a first domain key, a join domain response message including a domain ID field and a second domain key, wherein the domain ID field includes a ‘domain baseID’ for indicating an ID of a first domain among a plurality of domains managed by an entity, and wherein the join domain response message further includes a domain generation indicating a generation of the first domain; comparing the domain baseID of the domain ID field included in the join domain response message with a domain baseID of a domain ID stored in the terminal; if the domain baseID of the domain ID field included in the join domain response message is not consistent with the domain baseID stored in the terminal, performing a first procedure for joining the first domain; and if the domain baseID of the domain ID field included in the join domain response message is consistent with the domain baseID stored in the terminal, performing a second procedure for upgrading the first domain, wherein the second procedure includes: comparing the domain generation included in the join domain response message with a domain generation stored in the terminal; and storing the second domain key, which is contained in the join domain response message, based on a result from the comparison, wherein the first domain key is associated with the domain generation stored in the terminal and is maintained to allow the first rights object to be still used after upgrading the first domain, and wherein the received second domain key is associated with the domain generation included in the join domain response message and allows a second rights object to be used.

2. The method of claim 1 , wherein the join domain response message is based on a one-way protocol and is a ‘dmp Join Domain Response’ message.

3. The method of claim 1 , wherein the domain ID field corresponds to a ‘domain ID field’ in the join domain response message.

4. The method of claim 1 , wherein the server is a Right Issuer, or a Domain Authority/Domain Enforcement Agent (DA/DEA).

5. The method of claim 1 , the storing step is performed if the domain generation included in the join domain response message is greater than the domain generation stored in the terminal.

6. A domain upgrade method for a terminal, comprising: sending, to a terminal which wants to join into a first domain, a first join domain response message including a domain ID field and a first domain key, wherein the domain ID field comprises a ‘domain baseID’ element indicating an ID of the first domain among a plurality of domains and the first join domain response message further includes a ‘domain generation’ element indicating a first generation of the first domain; upgrading the first domain by generating a second domain key and a second generation of the first domain; and sending, to the terminal, a second join domain response message including the second domain key, wherein the second join domain response message further includes a domain ID field, wherein the domain ID field comprises a ‘domain baseID’ element indicating the same ID of the first domain, thereby to be compared with the domain baseID of the domain ID included in the first join domain response message and stored in the terminal, wherein the second join domain response message further includes a ‘domain generation’ element indicating the second generation, thereby to be compared with the ‘domain generation’ element included in the first join domain response message and stored in the terminal, wherein the first domain key is associated with the first generation and allows a first rights object (RO) to be used by the terminal, and wherein the second domain key is associated with the second generation and allows a second rights object (RO) to be used by the terminal.

7. The method of claim 6 , wherein the message is a ‘dmpJoinDomainResponse’ message.

8. The method of claim 6 , wherein the domain ID field corresponds to a ‘domID’ field in the message.

9. The method of claim 6 , wherein the upgrading step is performed if another terminal included in the domain is revoked by the server or the first domain key is compromised by the another terminal.

10. The method of claim 6 , wherein the second generation is generated by increasing the first domain generation by 1.

11. The method of claim 6 , wherein the second domain key included in the join domain response message had been upgraded from the first domain key by the server if another terminal included in the domain is revoked by the server or the first domain key is compromised by the another terminal, wherein the join domain response message is transmitted from the server to terminals which are still trusted by the server.

12. The method of claim 6 , wherein the join domain response message is transmitted from the server to terminals which are still trusted by the server.

13. A domain upgrade method for a terminal, comprising: receiving, by a terminal, a first join domain response message including a domain ID field and a first domain key, wherein the domain ID field includes a ‘domain baseID’ for indicating an ID of a first domain among a plurality of domains managed by an entity; if there does not exist a domain baseID matching with the domain baseID of the domain ID field included in the first join domain response message, performing a first procedure for joining the first domain thereby to obtain a first rights object (RO); consuming contents using the first RO; receiving, by the terminal, a second join domain response message including a domain ID field and a second domain key, wherein the domain ID field in the second join domain response message includes a ‘domain baseID’ for indicating the ID of the first domain; comparing the domain baseID of the domain ID field included in the second join domain response message with the domain baseID of the domain ID stored in the terminal; if the domain baseID of the domain ID field included in the second join domain response message is consistent with the domain baseID stored in the terminal, performing a second procedure for upgrading the first domain, wherein the second procedure includes: comparing a domain generation included in the second join domain response message with a domain generation stored in the terminal; and storing the second domain key, which is contained in the second join domain response message, based on a result from the comparison, wherein the first domain key is associated with the domain generation stored in the terminal and is maintained to allow the first rights object to be still used after upgrading the first domain, and wherein the received second domain key is associated with the domain generation included in the second join domain response message and allows a second rights object to be used.